Effect pigments are based on the use of a laminar substrate such as mica or perlite flakes which have been coated with metal oxide layer(s). These pigments can exhibit pearl-like luster as a result of reflection and refraction of light, and depending on the thickness of the metal oxide layer, they can also exhibit interference color effects.
DE102005025609 discloses non-metallic pigment mixtures with high metal brightness, useful e.g., in cosmetic, lacquers and colors, comprising gold color interference pigments and further pigments of silver-white, silver-gray and black-gray interference pigments.
EP1469042 discloses a pigment mixture comprising component A containing glass flakes based effect pigment(s) and component B containing organic and/or inorganic flake-form, needle-shaped, spherical or crystalline colorants and/or fillers. The admixture of one or more colorants to the coated glass flakes enables a rainbow effect to be imparted on the application systems, increases the color effect and achieves novel color effects.
WO2006110359 relates to an effect pigment comprising a synthetic platelet coated with a translucent metal oxide film, said synthetic platelet having a size distribution characterized as a D10 of at least 9.5 microns, a D50 of between about 20 and less than 40 microns, and a D90 of over 35 to less than 85 microns. The metal oxide film can comprise titanium dioxide, or iron oxide. The synthetic platelet is selected from aluminum oxide, silicon dioxide, bismuth oxychloride, boron nitride, and glass. WO2006110359 teaches how to modify the particle size distribution of a pigment in order to optimize sparkle effect.
Methods currently known in the art to make iron oxide coated perlite flakes and standard methods of coating mica and glass flakes with iron oxide are not effective because the iron oxide layer easily strips off of the substrate resulting in an undesirable product.
Accordingly, there is still a need in the art for effect pigments with high sparkle effect (i.e., no stripping of iron oxide from the substrate) that are still economical to produce.
It is thus an object of this invention to provide an effect pigment that has improved chromaticity and sparkle. It is another object of the present invention to develop effect pigments on the basis of a natural substrate (i.e., perlite flakes) that would exhibit advantages such as good application properties in a variety of compositions, environmental compatibility, and simple handling in conjunction with realizing superior optical effects, i.e., high sparkle effect.